I think the reason HBS, as well as many other schools, ask about mistakes and failures is because they want to see that you have the ability to learn from errors and/or problems. Clearly this is an important skill required for analyzing case studies.

I think it is important that we read what is written here very closely as it will help you see that there are multiple correct ways to answer this question. It is particularly important to differentiate between a failure and a mistake:

A mistake is wider in scope than a failure because not all mistakes necessarily lead to failure, though human failures are certainly the result of mistakes. A mistake may lead to a failure. A mistake may actually lead to a positive unintended outcome.

Notice that HBS does not say "your mistake." It is possible that the mistake you learned from might be one where you were an observer, a victim, and/or the source of the solution. That said, I can't recommend writing about a mistake where you blame someone else. After all, leaders take responsibility and if you are using one of your four essays to show why you are not responsible, I don't think you will be optimizing your chances for an interview invitation from HBS.

It is critical that you learned something meaningful about yourself. And your learning about yourself should be important, otherwise why tell admissions about it? Therefore the key constraint of this question is that whatever the mistake is, you have learned something important from it. While not stated, you may very well find that one way of showing what you learned is to discuss how you applied your lesson to a new situation.I would, in fact, argue that the heart of any sort of "failure question," whether it is an essay question or an interview is what you learned. Also depending on what your role was, how you reacted is also very important.

The basic components of an answer:
1. Clearly state what the mistake was.
2. Clearly state your role.
3. Explain how you reacted to the situation.
4. Explain what you learned.
5. If applicable, show how you applied what you learned to a new situation. Given the word count limitations, getting to this step can be challenging, but I highly recommend it.

The nice thing about mistakes is that everyone makes them. That said, if your mistake is terribly minor, it is unlikely to really to reveal anything significant. So focus on a big mistake where you really learned something. The word count is limited, but, if you can, show how you applied what you learned to a new situation because the application of abstract learning to a new situation is a key indicator of real learning. Think about really demonstrating the value of what you learned. In this regard, I think it is often the case that older mistakes make better topics because the post-mistake learning is likely to more effectively result in application to a new situation.

FALSE LEARNING
Every year as part of my reapplication counseling work, I read mistake/failure essays that are part of applications to schools like HBS, Wharton, and INSEAD. One major reason why a failure/mistake essay might not work well is false learning. False learning is any situation when you indicate that you learned something, but actually it was something that you already knew or others are likely to assume that you know. False learning tends to undermine the credibility of applicant in terms of their intelligence and honesty. It is thus best avoided. To avoid it, simply ask yourself whether you actually learned something new and were not merely reminded of the sort of thing you have learned while in kindergarten or soon thereafter.

Topic Selection
Pick a failure that you can be proud of and that ultimately shows you in positive light based on the understanding that you obtained and the maturity you demonstrated after the fact. The topic might be academic, personal, or professional. When you select the topic, think not only about the topic's significance, but also it's impact on overall balance within your essay set.

Mistake essays can be great opportunities to reveal something your approach to leadership or teamwork. Taking responsibility for a mistake, learning to communicate more effectively with others, gaining greater insight into how to influence others, and many other topics can be used effectively to highlight your leadership potential.

Some topics are best avoided. For example, it is usually unattractive to consider your employment termination due to entering into a particular job sector or for a particular employer as a mistake. Failed romantic relationship mistakes are even less likely to result in an effective HBS essay. Such topics might certainly be great moments of learning, but such topics rarely make good essays as they tend to have an undercurrent of regret, possibly anger, and often communicate nothing very positive about the applicant.

I hope you write about a great mistake successfully.

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